Generally, in automobiles with a gasoline engine or automobiles with a diesel engine, a generator is rotated so as to generate electricity with pulleys and a belt in conjunction with rotation motion by the crank mechanism of an engine, and the generated electricity is accumulated in a storage battery. Further, in railroad vehicles, in order to cover electric power for railroad passenger carriages which run by being towed with a locomotive engine, heretofore, the rotation of a wheel is transmitted to a generator via pulleys and a belt or gears and a universal joint, whereby the generator is rotated so as to generate electricity, and the generated electricity is used as it is, or the surplus is accumulated in a storage battery.
Incidentally, in the automobiles, except special electric automobiles, with a single motive power, a four-wheeled vehicle runs with four wheels, a three-wheeled vehicle runs with three wheels, and a two-wheeled vehicle runs with two wheels. Although the utilization of the rotation of this wheel enables electricity generation, conventionally, the installation of a generator on a wheel of an automobile has not been carried out generally due to the restriction in space.
FIG. 13 is a cross-sectional view for explaining a structure in a conventional attaching portion of a wheel (rear wheel) of a vehicle, herein an automobile.
As shown in FIG. 13, the wheel of an automobile is constituted with a tire wheel 4, a rim L disposed integrally on its outer peripheral surface, a tire T installed on the rim L, a tire drum 3 fixed to the tire wheel 4 with, for example, bolts and nuts (hub bolts 29 and hub nuts 30), and a wheel-axle flange 1a arranged to face the tire drum 3.
Here, for example, the tire wheel 4 of a rear wheel is coupled integrally to a rear wheel axle 2a, and the tire drum 3, the tire wheel 4, and the tire T are rotated with the rotation of the rear wheel axle 2a. In order to generate electricity by utilizing the rotation of a wheel axle (rear wheel axle 2a) of such an automobile, on a rotatable wheel (rear wheel) side and on a stationary side (collectively called as a wheel-axle portion, and a wheel and a wheel-axle portion are collectively called as an attaching portion of a wheel) which support the wheel, a rotor and a stator of a generator may be attached, respectively, so as to face each other.
For example, in the case where a generator is attached to a wheel-axle 2a portion of a rear wheel of a vehicle, if the generator is attached by reducing the length of the wheel-axle housing 1 and the rear wheel axle 2a, or a suspension, the generator can be installed without protruding from the rear wheel. In this case, the reduction of the length of the wheel-axle housing 1 and the rear wheel axle 2a, or the suspension causes a problem in which the running of the vehicle becomes unstable. Therefore, when the generator is attached without reducing their lengths, the generator protrudes from the vehicle body. However, on such a portion protruding from the vehicle body, it is sufficient that a tire house (fender) is mounted and side mirrors are extended to the left and right by a length corresponding to the portion.
Nevertheless, conventionally, even if a generator is attached to a vehicle axle to generate electricity, it has been difficult to find a generator suitable for the axle.